There exists in the oil and gas industry a procedure known as "snubbing" in which a string of pipe is forced into a wellhole under pressure for various reasons, such as, to remove an obstruction that might exist in the well. In such cases, the wellhole usually has been drilled and a certain amount of casing has been set and blowout preventors or other ram apparatus have been installed at the wellhead to seal around the drill pipe or other pipe strings being inserted into the wellhole. These blowout preventers and ram-type apparatus seal around the string of pipe being snubbed into the well under pressure to prevent the pressurized fluid from escaping around the outside of the string of pipe. In practice, the body of the individual segments of pipe comprising the string of pipe to be snubbed into the well usually are rack-tested hydrostatically or otherwise prior to use to make certain there are no leaks in the body of the pipe. However, as the connections between the various pipe segments are made-up and snubbed into the well, they are usually immediately subjected to high external pressures. The rack testing of the pipe segments will not reveal a leak that exists in a connection between two of the pipe segments. A leak in a connection creates a very hazardous working condition for all personnel involved as high-pressure fluid may flow from the inside of the wellhole, through the leak, upwardly through the string of pipe being snubbed into the well, and out onto the workmen. In addition, if corrective measures are required to correct the leak in a connection between the pipe segments after the string of pipe has been snubbed into the well, such corrective measures are expensive.
There also exists in the oil and gas industry a procedure known as the work-over of a well in which a string of pipe is forced into a previously drilled well. The well is "live," that is, contains fluid under pressure, below a certain depth but because of some obstruction, such as sand or concrete or the like, contains little or no pressurized fluid above that depth. When the tool on the end of the string of pipe breaks through the obstruction, the entire drill string, including the connections between the segments, is subject to the pressures of the well, which pressures can be intense. The same problems described above with respect to snubbing pipe into a completely live well, are applicable to this workover procedure. It is intended that the improved method and appartus shall be applicable to such a workover procedure and, as such, as used herein the word snubbing shall include not only inserting a string of pipe into a completely live well but also inserting a string of pipe into a well under circumstances in which the possibility exists that the string of pipe may be subjected to pressurized fluids.
It is an object of this invention to provide a method and apparatus for testing the connections between the pipe segments comprising a string of pipe being snubbed into a well under pressure immediately before such connections are forced into the pressurized well and thereby reducing hazardous working conditions by testing the connections for leaks after making them up and just prior to snubbing them in.
It is an additional object of this invention to provide an improved method and apparatus for snubbing a string of pipe into a well under pressure within a testing apparatus for externally testing the connections between the segments of pipe comprising the string of pipe is mounted for vertical movement above the blowout preventers or other ram-safety apparatus so that the connections between the pipe segments comprising the string of pipe may be tested immediately before such connections are forced into the pressurized well.
The invention itself, as well as additional objects and advantages thereof, will become readily apparant from the following description in connection with the accompanying drawings, in which like numerals represent like parts: